The present invention relates to the preparation of a polyolefin having end-functionalized branches, the intermediate products and the processes to obtain these products.
Commercially available polyethylene and polypropylene prepared using standard procedures with Ziegler-Natta or metallocene catalysts have a predominantly linear molecular structure. Although linear polyolefins have many desirable physical properties, they show a variety of melt processing shortcomings, especially the metallocene prepared ones having narrow molecular weight distributions, which typically have a low melt strength. Low melt strength is a problem because it causes local thinning in melt thermoforming, relative weakness in large-part blow molding and flow instabilities in co-extrusion of laminates.
One way of overcoming the shortcomings of linear polyolefins is by means of branching, viz. the provision of polymer side chains extending from the polyolefin backbone.
In the prior art different approaches have been developed to prepare branched polyolefins including methods based on chain transfer concepts.
Despite their ubiquitous presence in our society, polyolefins such as polyethylene and polypropylene are not appropriate for several applications as a consequence of their inherently nonpolar character. This nonpolar character is the reason for the poor adhesion, printability and compatibility that can restrict their efficacy. Hence, it is further desirable to prepare polyolefins having end-functionalized branches with for example polar end groups so that the polyolefins having end-functionalized branches also exhibit good adhesion and printability.
In the prior art different approaches have been developed to prepare polyolefins with functionalized branches. One method entails the copolymerization of olefins with protected heteroatom-containing functionalized olefin comonomers to afford after hydrolysis a short chain branched polyolefin with functionalized short chain branches. Alternatively, a copolymerization of an olefin and an aluminum-containing olefinic comonomer is carried out, which, after oxidation with oxygen, affords a short chain branched polyolefin with functionalized short chain branches.
This invention is directed towards an improved process for the preparation of branched polyolefins having end-functionalized branches.
With “polyolefin having branches” is meant a polyolefin having one or multiple branches.
It is an aim of the present invention to provide a process for the preparation of polyolefins having one or multiple main group metal end-functionalized branches.
It is an aim of the present invention to provide a process for the preparation of polyolefins having one or multiple end-functionalized branches.
It is moreover an aim of the present invention to provide polyolefins having one or multiple end-functionalized branches
One or more of these aims are obtained by the catalyst system according to the present invention.
One or more of these aims are obtained by the process according to the present invention.